The present invention relates to a tablet apparatus in which an operation panel or a supporting board for supporting the operation panel is vibrated when an inputting operation is conducted on the operation panel by an operator, so that the operator can have a feeling of inputting operation. More particularly, the present invention relates to a tablet apparatus in which an operation panel or a supporting board for supporting the operation panel is vibrated by a piezoelectric substrate.
The tablet apparatus is referred to as a digitizer, which is operated as follows. An indicating tool such as a stylus pen or a finger is made to come into contact with or come close to an operation panel supported by a supporting board. An input operating position on the operation panel, with which the indicating tool or the finer is made to come into contact or to which the indicating tool or the finger is made to come close to, is detected, and the input position data expressing the input operating position is outputted to a processing device such as a personal computer.
Especially when the operation panel, the supporting board, the insulating layer formed for detecting an input operating position and the electrode are made of transparent material, the tablet apparatus can be arranged on a display device such as a liquid crystal panel or CRT, and the inputting operation can be conducted on the inputting operation face of the tablet apparatus, that is, the inputting position data corresponding to a content on the display can be outputted into a processing device such as a personal computer while the operator is watching the content on the display.
Concerning the tablet apparatus, according to the system of detecting an input operating position on the operation panel, various tablet apparatus are proposed such as a magnetic coupling system disclosed in JP-A-5-289806, a capacity coupling system disclosed in JP-A-6-242875, a contact system disclosed in JP-UM-A-3-6731, a resistance system disclosed in JP-A-5-53715 and an optical coupling system disclosed in JP-UM-A-5-33235. However, in general, the operator can only know the result of operation by a processing device such as a personal computer, that is, it is impossible for the operator to know whether or not the inputting operation itself to the operation panel is detected by the tablet apparatus. Therefore, the operator feels uncertain about the inputting operation the operator has conducted.
The force feedback type tablet apparatus is known in which the operation panel of the supporting board is vibrated in response to the inputting operation so that the operator can feel that the inputting operation has been conducted into the tablet apparatus via a stylus pen or a finger, which comes into contact with the operation panel. Especially, the present applicant has developed a tablet apparatus in which the operation panel and the supporting board are effectively vibrated by a simple and compact structure in which a piezoelectric substrate is directly fixed to the operation panel or the supporting panel. Concerning this tablet apparatus, refer to Patent Document 1.
Patent Document 1: JP-A-2003-122507 (Abstract, FIG. 1)
FIG. 7 is a view showing this forced feedback type tablet apparatus 100, in which the operation panel 101 includes a flexible sheet made of plastics and the supporting board made of glass are laminated on each other leaving a small gap. In this structure, the tablet apparatus 100 is a resistance pressure sensitive system tablet apparatus, in which the conductive layers 101a, 102a formed of uniform resistance films are provided on the opposed face on which the operation panel 101 and the supporting board 102 are opposed to each other and uniform electric potential gradients are alternately formed on the conductive layers 101a, 102a. When the inputting operation is conducted by pushing a surface of the operation panel 101, the conductive layers 101a, 102a are contacted with and connected to each other at the input operating position, and an electric potential of the input operating position (the contact position) is read out from the other conductive layers 101a, 102a on which the electric potential gradient is not formed. In this way, the inputting operation and the input operating position are detected.
The piezoelectric substrate 103 is formed into a long and slender shape. A pair of drive electrodes 103a, 103b are provided on opposite faces of the piezoelectric substrate 103, and an entire face of one of opposite faces is fixed to the operation panel 101 or the supporting board 102 with adhesive. When it is detected that the inputting operation has been conducted on the inputting operation face 101c of the operation panel 101, a drive voltage is applied upon a pair of drive electrodes 103a, 103b. Due to the foregoing, the piezoelectric substrate 103 is expanded and contracted, and the operation panel 101 or the supporting board 102, to which the piezoelectric substrate 103 is fixed, is vibrated. By this vibration, the operator can confirm that the inputting operation has been accepted by the device.
According to this tablet apparatus 100, the long and slender piezoelectric substrate 103 is simply fixed to the operation panel 101 or the supporting board 102. Therefore, the entire structure can be made simple, and the operation panel 101 and the supporting board 102 can be vibrated by the simple structure without enlarging the size. Further, it is unnecessary to provide a vibration source and a transmission means for transmitting vibration from the vibration source to the operation panel 101 or the supporting board 102. Accordingly, it is possible to eliminate a loss of energy caused in the transmission of vibration. Further, it is possible to avoid the delay of transmission time of vibration.
Utilizing the electrostriction effect of the piezoelectric substrate 103 causes vibration of the operation panel 101 or the supporting board 102. A drive voltage is applied upon a pair of drive electrodes 103a, 103b, and one face of the piezoelectric substrate to expand and contract is fixed to the operation panel 101 or the supporting board 102, and the distortion is transmitted to the operation panel 101 or the supporting board 102, so that the operation panel 101 or the supporting board 102 can be vibrated.
By forming the piezoelectric substrate 103 into a long and slender shape, it is possible to obtain larger amplitude by a smaller quantity of vibration material. In the case where the operation panel 101 or the supporting board 102, to which the piezoelectric substrate 103 is fixed, is rectangular, when the long and slender piezoelectric substrate 103 is fixed along the longitudinal direction (direction X) as shown in FIG. 7, the operation panel 101 or the supporting board 102 can be vibrated by larger amplitude compared with the case where it is fixed along the lateral direction (direction Y).
On the other hand, concerning the fixing position of the piezoelectric substrate 103, an influence on the position detection of the inputting operating conducted on the inputting operation face 101c should be prevented and it should be avoided to arrange the piezoelectric substrate 103 below the inputting operation face 101c in the case of a tablet apparatus 100 made of transparent material because the operator is watching a display on the display device arranged on the back of the tablet apparatus to conduct the inputting operation. Therefore, the fixing position of the piezoelectric substrate 103 is arranged on one side of the operation panel 101 or the supporting board 102 in the longitudinal direction.
For the reasons described above, as shown in FIG. 7, the piezoelectric substrate 103 is fixed to one side of the operation panel 101 or the supporting board 102 in the longitudinal direction. However, in the case where the tablet apparatus 100 is attached to a housing not shown or a display device such as a liquid crystal panel supported by the housing, in order to vibrate the device as entirely as possible, four corners of the operation panel 101 or the supporting board 102 are attached to the housing or the display device. Therefore, depending upon a position at which the input operation is conducted, the operator cannot sufficiently have a feeling of inputting operation by the vibration in some areas.
FIG. 8 is a view showing the generation of vibration caused in the following circumstances. Under the condition of restricting the vibration of four corners, a drive voltage of 280V is applied upon the piezoelectric substrate 103 fixed to one side of the supporting board 102 in the longitudinal direction, and the supporting board 102 is vibrated. At this time, amplitude z at each position in direction Z perpendicular to the surface of the drawing is shown in FIG. 8. Amplitude z is increased in the order of z0, z1, z2 and z3. As can be seen in this drawing, amplitude z of the vibration generated on the supporting board 102 is largest at the center of the long and slender belt-shaped piezoelectric substrate 103. At a position distant from the center, amplitude z of the vibration generated on the supporting board 102 is reduced. Since the four corners are restricted, amplitude z in the vicinity of each corner is reduced. As a result, when the inputting operation is conducted on the left lower corner and the right lower corner, even if the supporting board 102 is vibrated, a sufficiently large vibration for the operator to have a feeling of inputting operation is not generated at the input operating position. Therefore, it is impossible for the operator to have a feeling of inputting operation.
Therefore, as shown in FIG. 9, the following attempt was made. A pair of piezoelectric substrates 103 is fixed to opposite sides of the supporting board 102 in the longitudinal direction, and the aforementioned non-sensitive region of one piezoelectric substrate 103 is compensated by the other piezoelectric substrate 103. FIG. 9 is a view showing a state in which a drive voltage is applied upon a pair of piezoelectric substrates 103 under the same condition as that of FIG. 8, and amplitude z at each position on the supporting board 102 is shown. In the drawing, amplitude z is increased in the order of z0, z1, z2 and z4. However, even when the pair of piezoelectric substrates 103 are used as described above, since no piezoelectric substrates 103 are provided at the four corners in the lateral direction (direction Y), the four corners still remain as non-sensitive regions.
Amplitude z of the vibration generated by the piezoelectric substrate 103 depends on the length of the long and slender belt-shaped piezoelectric substrate 103 in the longitudinal direction. Therefore, when the entire side of the operation panel 101 or the supporting board 102 in the longitudinal direction is fixed to the piezoelectric substrate 103, the above problems are solved. However, when a common piezoelectric substrate 103, the length of which is shorter than that in the longitudinal direction, is used in order to enhance the mass production effect or when a tablet apparatus having a large inputting operation face is used, it is not always possible to fix the piezoelectric substrate 103 to the entire length in the longitudinal direction.
An amplitude of the vibration generated by the piezoelectric substrate 103 is proportional to the voltage applied upon the piezoelectric substrate 103. However, when the voltage applied upon the piezoelectric substrate 103 is raised, an electric power consumption is increased, and the manufacturing cost is also increased by using a high voltage circuit. Therefore, it is necessary to maintain the voltage to be lower than a predetermined withstanding voltage.